1. Technical Field
The following description relates to one or more techniques that can make a hue deviation, which could be caused when a color image output device such as a color printer and a color display device expresses a gray color, less noticeable.
2. Related Art
There can be some cases where a color gamut that a color image output device such as a color printer and a color display device can output is narrower than a color gamut of input color image data. In order to solve the aforementioned problem, conventionally, there is performed data processing to convert the input color image data so as to conform the color gamut thereof to a color gamut of the color image output device. The color image output device then forms a color image based on the converted color image data (see Japanese Patent Provisional Publication No. 2000-253269).
Among various color image output devices, a printer expresses various colors by changing a ratio of four process colors (CMYK). However, there might be some cases where a ratio of the four process colors in an actually formed color image deviates from an ideal ratio set for the input color image data. For example, in a case of an inkjet printer, the ratio of the four process colors is adjusted by a discharge ratio of the four process colors that can be affected by a mechanical configuration of an inkjet head. For this reason, an actual discharge ratio of the four process colors could deviate from the ideal ratio set for the input color image data.
In this case, a color in the actually formed color image deviates from an ideal color to be expressed by the input color image data. Especially, a hue deviation of a gray color that could be caused by an image forming operation is likely to be noticeable in the actually formed color image, since even a slight hue deviation can cause a change of the gray color across an axis of a color space such as an L*a*b color space.